1. Field of the Invention
This invention is in the field of medicinal chemistry. In particular, the invention relates to substituted 2-aminoacetamides and the discovery that these compounds act as blockers of sodium (Na+) channels.
2. Related Background Art
Several classes of therapeutically useful drugs, including local anesthetics such as lidocaine and bupivacaine, antiarrhythmics such as propafenone and amioclarone, and anticonvulsants such as lamotrigine, phenytoin and carbamazepine, have been shown to share a common mechanism of action by blocking or modulating Na+ channel activity (Catterall, W. A., Trends Pharmacol Sci. 8:57-65 (1987)). Each of these agents is believed to act by interfering with the rapid influx of Na+ ions.
Recently, other Na+ channel blockers such as BW619C89 and lifarizine have been shown to be neuroprotective in animal models of global and focal ischemia and are presently in clinical trials (Graham et al., J. Pharmacol. Exp. Ther. 269:854-859 (1994); Brown et al., British Pharmacol. 115:1425-1432 (1995); SCRIP 1870:8 (1993); SCRIP 1773:14 (1992)).
The neuroprotective activity of Na+ channel blockers is due to their effectiveness in decreasing extracellular glutamate concentration during ischemia by inhibiting the release of this excitotoxic amino acid neurotransmitter. Studies have shown that unlike glutamate receptor antagonists, Na30  channel blockers prevent hypoxic damage to mammalian white matter (Stys et al., J. Neurosci. 12:430-439 (1992)). Thus, they may offer advantages for-treating certain types of strokes or neuronal trauma where damage to white matter tracts is prominent.
Another example of clinical use of a Na+ channel blocker is riluzole. This drug has been shown to prolong survival in a subset of patients with ALS (Bensimm et al., New Engl. J. Med. 330:585-591 (1994)) and has subsequently been approved by the FDA for the treatment of ALS. In addition to the above-mentioned clinical uses, carbamazepine, lidocaine and phenytoin are occasionally used to treat neuropathic pain, such as from trigeminal neurologia, diabetic neuropathy and other forms of nerve damage (Taylor and Meldrum, Trends Pharmacol. Sci. 16:309-316 (1995)), and carbamazepine and lamotrigine have been used for the treatment of manic depression (Denicott et al., J. Clin. Psychiatry 55: 70-76 (1994)).
It has been established that there are at least five to six sites on the voltage-sensitive Na channels which bind neurotoxins specifically (Catterall, W. A., Science 242:50-61 (1988)). Studies have further revealed that therapeutic antiarrhythmics, anticonvulsants and local anesthetics whose actions are mediated by Na+ channels, exert their action by interacting with the intracellular side of the Na+ channel and allosterically inhibiting interaction with neurotoxin receptor site 2 (Catterall, W. A., Ann. Rev. Pharmacol Toxicol. 10:15-43 (1980)).
PCT International Published Application WO 90/14334 and WO 97/05102 disclose 2-(4-substituted)-benzylamino-2-methyl-propanamide derivatives represented by Formula I: 
where n is 0-3; X is O, S, CH2 or NH; each of R and R1 independently is hydrogen, C, alkyl, halogen, hydroxy, C1-4 alkoxy, or trifluoromethyl; each of R2, R3 and R4 independently is hydrogen, C1-6 alkyl or C3-7 cycloalkyl: The compounds are disclosed to be useful as antiepileptics, in the treatment of Parkinson""s disease and as neuroprotective agents, e.g. preventing or treating neuronal loss associated with stroke, hypoxia, ischemia, CNS trauma, hypoglycemia or surgery, and in treating and preventing neurodegenerative diseases such as Alzheimer""s disease, amyotrophic lateral sclerosis, Down""s syndrome, Huntington""s disease, dementia caused by acquired immunodeficiency syndrome (AIDS), infarctual dementia and infections or inflammations in the brain; they can also be used as antidepressants, hypnotics, and antispastic agents and in treating ocular damage and retinopathy. However, their mechanism of action was not disclosed.
The present invention is related to treating a disorder responsive to the blockade of sodium channels in a mammal suffering from excess activity of said channels by administering an effective amount of a compound of Formula I. The present invention is also related to treating a disorder responsive to the blockade of sodium channels in a mammal suffering therefrom by administering an effective amount of a compound of Formula II as described herein.
The present invention is also directed to the use of a compound of Formulae I or II for the treatment of neuronal damage following global and focal ischemia, and for the treatment or prevention of neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS), as antimanic depressants, as local anesthetics, as antiarrhythmics and for the treatment or prevention of diabetic neuropathy and for the treatment of pain including chronic pain.
The present invention also is directed to the process for preparing novel substituted 2-aminoacetamide of Formula II.
A first aspect of the present invention is directed to the use of compounds of Formulae I or II as blockers of sodium channels.
A second aspect of the present invention is to provide a method for treating, preventing or ameliorating neuronal loss following global and focal ischemia; treating, preventing or ameliorating pain including chronic pain; treating, preventing or ameliorating neurodegenerative conditions; treating, preventing or ameliorating manic depression; inducing local anesthesia; and treating arrhythmias by administering a compound of Formulae I or II to a mammal in need of such treatment.
A number of compounds within the scope of the present invention are novel compounds. Therefore, a third aspect of the present invention is to provide novel compounds of Formula II, and to also provide for the use of these novel compounds for treating, preventing or ameliorating convulsions.
A fourth aspect of the present invention is to provide a pharmaceutical composition useful for treating disorders responsive to the blockade of sodium ion channels, containing an effective amount of a compound of Formulae I or II in a mixture with one or more pharmaceutically acceptable carriers or diluents.
A fifth aspect of the present invention is directed to methods for preparing novel compounds of Formulae II.
The present invention arises out of the discovery that compounds of Formulae I and II act as blocker of the Na+ channel. In view of this discovery, compounds of Formulae I and II are useful for treating disorders responsive to the blockade of sodium ion channels.
The compounds useful in this aspect of the present invention are substituted 2-aminoacetamides represented by Formula II: 
or a pharmaceutically acceptable salt or prodrug thereof, wherein:
R1, R2, R3 and R4 are independently hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl;
R5, R6 and R7 are independently hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl, or R5, is defined as above, and R6 and R7 together with the nitrogen atom to which they are attached form a heterocycle;
A1 and A2 are independently aryl, heteroaryl, saturated or partially unsaturated carbocycle or saturated or partially unsaturated heterocycle, any of which is optionally substituted;
X is one or O, S, NR8, CH2, C(O), NR8C(O), C(O)NR8, SO, SO2 or a covalent bond; where
R8 is hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl;
n is 0, 1, 2 or 3.
Preferred compounds falling within the scope of Formula II include compounds wherein A1 and A2 are both aryl moieties, preferably both phenyl moieties, that are each optionally independently substituted by one or two substituents independently selected from the group consisting of halogen, nitro, amino, C1-6 alkyl, C3-8cycloalkyl, cyano, C1-6 alkoxy or C6-10aryloxy; R1 is hydrogen, C1-6 alkyl, C3-8cycloalkyl or C6-10aryl; O or S.
Preferred compounds within Formula II also include those compounds where A1 is an optionally substituted aryl group selected from the group consisting of phenyl and naphthyl, and A2 is an optionally substituted heteroaryl or aryl group selected from the group consisting of pyridyl. pyrimidinyl, 1,3,5-triazinyl, furanyl, thiophenyl, naphthyl, quinolyl, 3,4-methylenedioxyphenyl, 3,4-ethylenedioxyphenyl, indanyl, tetrahydronaphthyl, biphenylmethyl, triphenylmethyl and quinoxalinyl.
Additional preferred compounds within Formula II also include those compounds where A1 is an optionally substituted aryl group selected from the group consisting of phenyl or naphthyl, and A2 is an optionally substituted carbocycle or heterocycle selected from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, piperidinyl, morpholinyl, pyrrolidinyl, tetrahydrofuranyl, tetrahydropyranyl, cyclohexenyl, adamantyl, exo-norbomyl and cyclopentenyl.
Additional preferred compounds within Formula II include those compounds where A1 is an optionally substituted heteroaryl or aryl group selected from the group consisting of pyridyl, pyrimidinyl, 1,3,5-triazinyl, naphthyl, quinolyl, furanyl, and thiophenyl, and A2 is an optionally substituted heteroaryl or aryl group selected from the group consisting of phenyl, furanyl, thiophenyl, quinolinyl, 3,4-methylenedioxyphenyl, 3,4-ethylenedioxyphenyl, indanyl, tetrahydronaphthyl and naphthyl.
Additional preferred compounds within Formnula II include those compounds where A1 is an optionally substituted, saturated or partially unsaturated carbocycle or heterocycle selected from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, morpholinyl, piperidinyl, pyrrolidinyl, tetrahydrofuranyl and tetrahydropyranyl, and A2 is an optionally substituted aryl or heteroaryl group selected from the group consisting of phenyl, furanyl, thiophenyl, quinolinyl, 3,4-methylenedioxyphenyl, 3,4-ethylenedioxyphenyl, indanyl, tetrahydronaphthyl, or naphthyl.
Exemplary preferred compounds that may be employed in this method of invention include, without limitation:
2-(4-(2-fluorobenzyloxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-methylenedioxyphenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-methylenedioxybenzyloxy)benzylamino)-2-methyl-propanamide;
2-(4-cyclohexyloxybenzylamino)-2-methyl-propanamide;
2-(4-(5,6,7,8-tetrahydro-2-naphthoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2-adamantanoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-Chloro-2-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2,4-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(6-bromo-4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-nitrophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-tetrahydropyranoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,5-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-chlorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-methylphenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2-chloro-4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(5-indanoxy)benzylamino)-2-methyl-propanamide;
2-(4-cycloheptoxybenzylamino)-2-methyl-propanamide;
2(4-(1-methyl-4-piperidinoxy)benzylamino)-2-methyl-propanamide,
2-(4-(exo-2-norbornoxy)benzylamino)-2-methyl-propanamide;
2(3-(4-fluorophenoxy)-5-pyridylmethylamino)-2-methyl-propanamide;
2-(4-(4-pyridinoxy)benzylamino)-2-methyl-propanamide;
2-(3-fluoro-4-(4-fluorophenyl)benzylamino)-2-methyl-propanamide,
2-(4-(2-pyrimidinoxy)benzylamino)-2-methyl-propanamide;
2-(4-(6-quinolinoxy)benzylamino)-2-methyl-propanamide;
2-(4-(N,N-diphenylamino)benzylamino)-2-methyl-propanamide;
2-(4-diphenylmethoxy)benzylamino-2-methyl-propanamide; and
2-(4-triphenylmethoxy)benzylamino-2-methyl-propanamide.
Since the compounds of Formula I and II are blockers of sodium (Na30 ) channels, a number of diseases and conditions mediated by sodium ion influx can be treated employing these compounds. Therefore, the invention is related to a method of treating, preventing or ameliorating neuronal loss associated with stroke, global and focal ischemia, CNS trauma, hypoglycemia and surgery, spinal cord trauma, as well as treating or ameliorating neurodegenerative diseases including Alzheimer""s disease, amyotrophic lateral sclerosis, Parkinson""s disease, treating or ameliorating anxiety, convulsions, glaucoma, migraine headache, and muscle spasm. The compounds of Formula I and II are also useful as antimanic depressants, as local anesthetics, and as antiarrhythmics; as well as for treating, preventing or ameliorating pain including surgical, chronic and neuropathic pain. In each instance, the methods of the present invention require administering to an animal in need of such treatment an effective amount of a sodium channel blocker of the present invention, or a pharmaceutically acceptable salt or prodrug thereof.
The present invention is also directed to novel compounds within the scope of Formula II. These compounds include those compounds of Formula II where:
R1, R2, R3 and R4 are independently hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl;
R5, R6 and R7 are independently hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl, or R5, is defined as above, and R6 and R7 together with the nitrogen atom to which they are attached form a heterocycle, including piperidine, piperazine, morpholine;
A1 and A2 are independently aryl, heteroaryl, saturated or partially unsaturated carbocycle or saturated or partially unsaturated heterocycle, any of which is optionally substituted;
X is one or O, S, NR8, CH2, C(O), NR8C(O), C(O)NR8, SO, SO2 or a covalent bond, where
R8 is hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, haloalkyl, aryl, aminoalkyl, hydroxyalkyl, alkoxyalkyl or carboxyalkyl;
n is 1, 2 or 3,
provided that:
when X is O, S, CH2 or NH; R1 and R2 are hydrogen, R3 and R4 are methyl or ethyl, then A1 and A2 are not both phenyl.
Specifically, preferred substituted 2-aminoacetamides are represented by Formulae III-VIII. In particular, a preferred embodiment is represented by Formulae III and IV: 
or a pharmaceutically acceptable salt or prodrug thereof, wherein R1, R2, R3, R4, R5, R6, R7, X, n, A1 and A2 are as defined previously with respect to Formula II; and
R9, R10, R11 and R12 independently are hydrogen, halo, haloalkyl, aryl, cycloalkyl, saturated or partially unsaturated heterocycle, heteroaryl, alkyl, alkenyl, alkynyl, arylalkyl, arylalkenyl, arylalkynyl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, cycloalkylalkyl, heterocycloalkyl, hydroxyalkyl, aminoalkyl, carboxyalkyl, alkoxyalkyl, nitro, amino, ureido, cyano, acylamido, hydroxy, thiol, acyloxy, azido, alkoxy, carboxy, carbonylamido or alkylthiol; or
R9, and R10, or R11 and R12 are taken together with the carbon atoms to which they are attached to form a carbocycle or heterocycle. Examples of bridges formed by R9 and R10 or R11 and R12 taken together are xe2x80x94OCH2Oxe2x80x94, xe2x80x94OCF2Oxe2x80x94, xe2x80x94(CH2)3xe2x80x94, xe2x80x94CH2)4xe2x80x94, xe2x80x94OCH2CH2Oxe2x80x94, xe2x80x94CH2N(R18)CH2xe2x80x94, xe2x80x94CH2CH2N(R18)CH2xe2x80x94, xe2x80x94CH2N(R18)CH2CH2xe2x80x94 and xe2x80x94CHxe2x95x90CHxe2x80x94CHxe2x95x90CHxe2x80x94; where R18 is hydrogen, alkyl or cycloalkyl;
provided that when A1 in Formula III is an optionally substituted phenyl, then R9 and R10 or R11 and R12 are taken together with the carbon atoms to which they are attached to form a carbocycle or heterocycle.
R13, R14, R15, R16 and R17 independently are hydrogen, halo, haloalkyl, aryl, cycloalkyl, saturated or partially unsaturated heterocycle, heteroaryl, alkyl, alkenyl, alkynyl, arylalkyl, arylalkenyl, arylalkynyl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, cycloalkylalkyl, heterocycloalkyl, hydroxyalkyl, aminoalkyl, carboxyalkyl, alkoxyalkyl, nitro, amino, ureido, cyano, acylamido, hydroxy, thiol, acyloxy, azido, alkoxy, carboxy, carbonylamido or alkylthiol; or
one of R13 and R14, or R14 and R15, or R15 and R16, or R16 and R17 are taken together with the carbon atoms to which they are attached to form a carbocycle or heterocycle. Examples of bridges formed by R13 and R14, or R14 and R15, or R15, and R16, or R16 and R17 taken together are xe2x80x94OCH2xe2x80x94, xe2x80x94OCF2Oxe2x80x94, xe2x80x94(CH2)3xe2x80x94, xe2x80x94(CH2)4xe2x80x94, xe2x80x94OCH2CH2Oxe2x80x94, xe2x80x94CH2N(R18)CH2xe2x80x94, xe2x80x94CH2CH2N(R18)CH2xe2x80x94, xe2x80x94CH2N(R18)CH2CH2xe2x80x94 and xe2x80x94CHxe2x95x90CHxe2x80x94CHxe2x95x90CHxe2x80x94; where R18 is hydrogen, alkyl or cycloalkyl.
provided that when A1 in Formula IV is an optionally substituted phenyl, then R13 and R14, or R14 and R15, or R15 and R16, or R16 and R17 are taken together with the carbon atoms to which they are attached to form a carbocycle or heterocycle.
Preferred values of A2 in Formula III include furanyl, thiophenyl, quinolinyl, 3,4-methylenedioxyphenyl, 3,4-ethylenedioxyphenyl, indanyl, tetrahydronaphthyl, and naphthyl.
Preferred values of A1 in Formula IV include furanyl, thiophenyl, quinolinyl, 3,4-methylenedioxyphenyl, 3,4-ethylenedioxyphenyl, indanyl, tetrahydronaphthyl and naphthyl.
Another preferred embodiment of the invention includes substituted 2-aminoacetamides represented by Formula V and Formula VI: 
or a pharmaceutically acceptable salt or prodrug thereof, wherein
R1xe2x80x94R7, R9-R12, R13-R17, n and X are as defined previously with respect to Formulae II, III and IV; and
A, B, C, D and E are independently nitrogen or carbon, provided that no more than three of A, B, C, D and E are nitrogen, and there is no substituent, except for oxygen (when the nitrogen is present as a N-oxide), present on A, B, C, D or E when said A, B, C, D or E represents nitrogen.
Preferred compounds of Formula V are those where one, two or three of A through E are nitrogens. Preferred compounds of Formula VI are those where one or two of A through D are nitrogens.
Another preferred embodiment of the invention includes substituted 2-aminoacetamide represented by Formula VII and Formula VIII: 
or a pharmaceutically acceptable salt or prodrug thereof, wherein R1-R7, R9-R12, R13-R17, n and X are as defined previously with respect to Formulae II, III and IV; and
B1 is an optionally substituted saturated or partially unsaturated carbocycle or optionally substituted, saturated or partially unsaturated heterocycle; and
B2 is an optionally substituted, saturated or partially unsaturated carbocycle or optionally substituted, saturated or partially unsaturated heterocycle.
Preferred B1 and B2 independently include cyclopentyl, cyclohexyl, cycloheptyl, tetrahydrofuranyl, tetrahydropyranyl, pyrrolidinyl and piperidinyl.
Generally, preferred compounds of Formulae II-VIII are those compounds where R1 and R2 is hydrogen or alkyl, more preferably hydrogen, methyl or ethyl, and where R3 and R4 are independently hydrogen or C1-4 alkyl.
Preferred values of X in Formulae II-VIII are O and S.
Preferred values of R5-R7 with respect to Formulae II-VIII are hydrogen or C1-4 alkyl.
Preferred values of R9-R12, and R13-R17, with respect to Formulae II-VIII include hydrogen, halo, C1-C6 haloalkyl, C6-C10 aryl, C4-C7 cycloalkyl, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C6-C10 aryl(C1-C6)alkyl, C6-C10 aryl(C2-C6)alkenyl, C6-C10aryl(C,xe2x80x94C6)alkynyl, C1-C6 hydroxyalkyl, nitro, amino, ureido, cyano, C1-C6 acylamido, hydroxy, thiol, C1-C6 acyloxy, azido, C1-C6 alkoxy, and carboxy. Alternatively, R9 and R10 or R11, and R12, or two adjacent R13 through R17 can form a bridge selected from the group consisting of xe2x80x94OCH2Oxe2x80x94, xe2x80x94(CH2)3xe2x80x94, xe2x80x94(CH2)4xe2x80x94, xe2x80x94OCH2CH2Oxe2x80x94, xe2x80x94CH2N(R18)CH2xe2x80x94, xe2x80x94CH2CH2N(R18)CH2xe2x80x94, xe2x80x94CH2N(R18)CH2CH2xe2x80x94, and xe2x80x94CHxe2x95x90CHxe2x80x94CHxe2x95x90CHxe2x80x94, where R18 is hydrogen or C1-C6 alkyl. Most preferably, at least one, two or three of R9, R10, R11, R12 are hydrogen. Most preferably, at least one, two or three of R13 through R17 are hydrogen.
With respect to the novel methods of treatment of the present invention, an additional preferred subset of substituted 2-aminoacetamide compounds includes compounds of Formula II, wherein A1 and A2 are phenyl moieties, that A2 is substituted by one or two substituents independently selected from the group consisting of hydrogen, C1-6 alkyl, halogen, hydroxy, C1-4 alkoxy, or trifluoromethyl; each of R1 and R2 are hydrogen; R3 and R4 are methyl; and R5-R7 are independently C1-6 alkyl or C3-7cycloalkyl.
Useful compounds in this aspect of the present invention include:
2-(4-(2-fluorobenzyloxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-methylenedioxyphenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-methylenedioxybenzyloxy)benzylamino)-2-methyl-propanamide.
2-(4-cyclohexyloxybenzylamino)-2-methyl-propanamide;
2-(4-(5,6,7,8-tetrahydro-2-naphthoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2-adamantanoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-Chloro-2-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2,4-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,4-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(6-bromo-4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-nitrophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-tetrahydropyranoxy)benzylamino)-2-methyl-propanamide;
2-(4-(3,5-difluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-chlorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(4-methylphenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(2-chloro-4-fluorophenoxy)benzylamino)-2-methyl-propanamide;
2-(4-(5-indanoxy)benzylamino)-2-methyl-propanamide;
2-(4-cycloheptoxybenzylamino)-2-methyl-propanamide;
2-(4-(1-methyl-4-piperidinoxy)benzylamino)-2-methyl-propanamide;
2-(4-(exo-2-norbornoxy)benzylamino)-2-methyl-propanamide;
2-(3-(4-fluorophenoxy)-5-pyridylmethylamino)-2-methyl-propanamide;
2-(4-(4-pyridinoxy)benzylamino)-2-methyl-propanamide;
2-(3-fluoro4-(4-fluorophenyl)benzylamino)-2-methyl-propanamide;
2-(4-(2-pyrimidinoxy)benzylamino)-2-methyl-propanamide;
2-(4-(6-quinolinoxy)benzylamino)-2-methyl-propanamide;
2-(4-(N,N-diphenylamino)benzylamino)-2-methyl-propanamide;
2-(4-diphenylmethoxy)benzylamino-2-methyl-propanamide; and
2-(4-triphenylmethoxy)benzylamino-2-methyl-propanamide.
Useful aryl groups are C6-14 aryl, especially C6-10 aryl. Typical C6-14 aryl groups include phenyl, naphthyl, phenanthryl, anthracyl, indenyl, azulenyl, biphenyl, biphenylenyl and fluorenyl groups.
Useful cycloalkyl groups include C3-8 cycloalkyl groups. Typical cycloalkyl groups include cyclopropyl, cyclobutyl, cyctopentyl and cyclohexyl and cycloheptyl.
Useful saturated or partially saturated carbocyclic groups are cycloalkyl groups as defined above, as well as cycloalkenyl groups, such as cyclopentenyl, cycloheptenyl and cyclooctenyl.
Useful halo or halogen groups include fluorine, chlorine, bromine and iodine.
Useful alkyl groups include straight-chained and branched C1-10 alkyl groups, more preferably C1-6 alkyl groups. Typical C1-10 alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, 3-pentyl, hexyl and octyl groups. Also contemplated is a trimethylene group substituted on two adjoining positions on the benzene ring of the compounds of the invention.
Useful alkenyl groups include C2-6 alkenyl groups, preferably C2-4 alkenyl. Typical C2-4 alkenyl groups include ethenyl, propenyl, isopropenyl, butenyl, and sec.-butenyl.
Useful alkynyl groups include C2-6 alkynyl groups, preferably C2-4 alkynyl. Typical C2-4 alkynyl groups include ethynyl, propynyl, butynyl, and 2-butynyl groups.
Useful arylalkyl groups include any of the above-mentioned C1-10 alkyl groups substituted by any of the above-mentioned C6-14 aryl groups. Typical groups include benzyl, phenethyl and naphthylmethyl.
Useful arylalkenyl groups include any of the above-mentioned C2-4 alkenyl groups substituted by any of the above-mentioned C6-14 aryl groups.
Useful arylalkynyl groups include any of the above-mentioned C2-4 alkynyl groups substituted by any of the above-mentioned C6-14 aryl groups. Typical groups include phenylethynyl and phenylpropynyl.
Useful cycloalkylalkyl groups include any of the above-mentioned C1-10 alkyl groups substituted by any of the above-mentioned cycloalkyl groups.
Useful haloalkyl groups include C1-10 alkyl groups substituted by one or more fluorine, chlorine, bromine or iodine atoms, e.g. fluoromethyl, difluoromethyl, trifluoromethyl, pentafluoroethyl, 1,1-difluoroethyl and trichloromethyl groups.
Useful hydroxyalkyl groups include C1-10 alkyl groups substituted by hydroxy, e.g. hydroxymethyl, hydroxyethyl, hydroxypropyl and hydroxybutyl groups.
Useful alkoxy groups include oxygen substituted by one of the C1-10 alkyl groups mentioned above.
Useful alkylthio groups include sulphur substituted by one of the C1-10 alkyl groups mentioned above.
Useful acylamino groups are any C1-6 acyl (alkanoyl) attached to an amino nitrogen, e.g. acetamido, propionamido, butanoylamido, pentanoylamido, hexanoylamido as well as aryl-substituted C2-6 substituted acyl groups.
Useful acyloxy groups are any C1-6 acyl (alkanoyl) attached to an oxy (xe2x80x94Oxe2x80x94) group, e.g. acetoxy, propionoyloxy, butanoyloxy, pentanoyloxy, hexanoyloxy and the like.
Useful saturated or partially saturated heterocyclic groups include tetrahydrofuranyl, pyranyl, piperidinyl, piperizinyl, pyrrolidinyl, imidazolidinyl, imidazolinyl, indolinyl, isoindolinyl, quinuclidinyl, morpholinyl, isochromanyl, chromanyl, pyrazolidinyl and pyrazolinyl groups.
Useful heterocycloalkyl groups include any of the above-mentioned C1-10 alkyl groups substituted by any of the above-mentioned heterocyclic groups.
Useful heteroaryl groups include any one of the following: thienyl, benzo[b]thienyl, naphtho[2,3-b]thienyl, thianthrenyl, furyl, pyranyl. isobenzofuranyl, chromenyl, xanthenyl, phenoxanthiinyl, 2H-pyrrolyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, 3H-indolyl, indolyl, indazolyl, purinyl, 4H-quinolizinyl, isoquinolyl, quinolyl, phthalzinyl, naphthyridinyl, quinozalinyl, cinnolinyl, pteridinyl, 5aH-carbazolyl, carbazolyl, xcex2-carbolinyl, phenanthridinyl, acrindinyl, perimidinyl, phenanthrolinyl, phenazinyl. isothiazolyl, phenothiazinyl, isoxazolyl, furazanyl, phenoxazinyl, 1,4-dihydroquinoxaline-2,3-dione, 7-aminoisocownarin, pyrido[1,2-a]pyrimidin4-one, 1,2-benzoisoxazol-3-yl, 4-nitrobenzofurazan. benzimidazolyl, 2-oxindolyl and 2-oxobenzimidazolyl. Where the heteroaryl group contains a nitrogen atom in a ring, such nitrogen atom may be in the form of an N-oxide, e.g. a pyridyl N-oxide, pyrazinyl N-oxide, pyrimidinyl N-oxide and the like.
Useful heteroarylalkyl groups include any of the above-mentioned C1-10 alkyl groups substituted by any of the above-mentioned heteroaryl groups.
Useful heteroarylalkenyl groups include any of the above-mentioned C2-4 alkenyl groups substituted by any of the above-mentioned heteroaryl groups.
Useful heteroarylalkynyl groups include any of the above-mentioned C2-4 alkynyl groups substituted by any of the above-mentioned heteroaryl groups.
Useful amino groups include xe2x80x94N2H, xe2x80x94NHR19, and xe2x80x94NR19R20, wherein R19 and R20 are C1-10 alkyl or cycloalkyl groups as defined above.
Useful aminocarbonyl groups are carbonyl groups substituted by xe2x80x94NH2, xe2x80x94NHR19, and xe2x80x94NR19R20, wherein R19 and R20 are C1-10 alkyl groups.
Optional substituents on any of the aryl, heterocyclic, heteroaryl, and cycloalkyl rings in Formulae II-VIII include any one of halo, haloalkyl, aryl, heterocycle, cycloalkyl, heteroaryl, alkyl, alkenyl, alkynyl, arylalkyl, arylalkenyl, arylalkynyl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, cycloalkylalkyl, heterocycloalkyl, hydroxyalkyl, aminoalkyl, carboxyalkyl, alkoxyalkyl, nitro, amino, ureido, cyano, acylamino, hydroxy, thiol, acyloxy, azido, alkoxy, carboxy, aminocarbonyl, and alkylthiol groups mentioned above. Preferred optional substituents include: halo, haloalkyl, hydroxyalkyl, aminoalkyl, nitro, alkyl, alkoxy and amino.
Certain of the compounds of Formula II may exist as optical isomers and the invention includes both the racemic mixtures of such optical isomers as well as the individual entantiomers that may be separated according to methods that are well known to those of ordinary skill in the art.
Examples of pharmaceutically acceptable addition salts include inorganic and organic acid addition salts such as hydrochloride, hydrobromide, phosphate, sulphate, citrate, lactate, tartrate, maleate, fumarate, mandelate, acetic acid, dichloroacetic acid and oxalate.
Examples of prodrugs include esters or amides of Formula II with R1-R7 as hydroxyalkyl or aminoalkyl, and these may be prepared by reacting such compounds with anhydrides such as succinic anhydride.
The invention is also directed to a method for treating disorders responsive to the blockade of sodium channels in animals suffering thereof. Particular preferred embodiments of the substituted 2-aminoacetamide for use in method of this invention are represented by previously defined Formula II.
The compounds of this invention may be prepared using methods known to those skilled in the art, or by the novel methods of this invention. The methods described in PCT published application WO97/05102, can be employed to synthesize compounds within the scope of the invention.
Compounds with Formulae II-VIII can be prepared as illustrated by exemplary reactions in Schemes 1-5. 
The compounds of the present invention were assessed by electrophysiological assays in dissociated hippocampal neurons for sodium channel blocker activity. These compounds also could be assayed for binding to the neuronal voltage-dependent sodium channel using rat forebrain membranes and [3H]BTX-B.
Sodium channels are large transmembrane proteins that are expressed in various tissues. They are voltage sensitive channels and are responsible for the rapid increase of Na+ permeability in response to depolarization associated with the action potential in many excitable cells including muscle, nerve and cardiac cells.
One aspect of the present invention is the discovery of the mechanism of action of the compounds herein described as specific Na+ channel blockers. In one aspect of the present invention it has been discovered that compounds disclosed in international published application WO 97/05102 are specific Na+ channel blockers. Based upon the discovery of this mechanism, these compounds, as well as novel compounds described herein, are contemplated to be useful in treating or preventing neuronal loss due to focal or global ischemia, and in treating or preventing neurodegenerative disorders including ALS, anxiety, and epilepsy. They are also expected to be effective in treating, preventing or ameliorating neuropathic pain, surgical pain and chronic pain. The compounds are also expected to be useful as antiarrhythmics, anesthetics and antimanic depressants.
The present invention is directed to compounds of Formulae II that are blockers of voltage-sensitive sodium channels. According to the present invention, those compounds having preferred sodium channel blocking properties exhibit an IC50 of about 100 xcexcM or less in the electrophysiological assay described herein. Preferably, the compounds of the present invention exhibit an IC50 of 10 xcexcM or less. Most preferably, the compounds of the present invention exhibit an IC50 of about 1.0 xcexcM or less. Substituted 2-aminoacetamide disclosed in WO 97/05102, as well as novel compounds of the present invention, may be tested for their Na+ channel blocking activity by the following electrophysiological and binding assays.
Electrophysiological Assay
Cell preparation: Acute cultures of rat hippocamnpal neurons were prepared daily using a modification of procedures described previously (Kuo and Bean, Mol. Pharm. 46:716-725 (1994)). Briefly, hippocampi were isolated from 3-11 day old rat pup brains (Sprague-Dawley; Charles River) and were sectioned, by hand, into 0.5-1 mm thick transyerse slices (Whittemore and Koerner, Eur. J. Pharm. 192:435-438 (1991)). Slices were incubated for at least 30 min at room temperature (20-24xc2x0 C.) in an oxygenated medium (124 mM NaCl, 3.3 mM KCl, 2.4 mM MgSO4, 2.5 mM CaCl2, 1.2 mM KH2PO4, 26 mM NaHCO3, pH=7.4) continuously bubbled with 5% CO2/95% O2. Prior to recording, 4-5 slices were transferred to an oxygenated dissociation medium (82 mM NaSO4, 30 mM K2SO4, 3 mM MgCl2, 2 mM HEPES, 26 mM NaHCO3, 0.001% phenol red, pH=7.4) containing 3 mg/mL protease XXIII (Sigma, St. Louis, Mo.) and incubated for 10-15 min at 37xc2x0 C., while continuously bubbling with 5% CO2/95% O2. Enzymatic digestion was terminated by transferring the slices to dissociation medium without bicarbonate, supplemented with 1 mg/mL bovine serum albumin and 1 mg/mL trypsin inhibitor (Sigma, St. Louis, Mo.). Slices were then transferred to a 35 mm culture dish containing dissociation medium without bicarbonate, and triturized with a fire-polished glass Pasteur pipette to release single cells. Cells were allowed to settle in this dish for 30 minutes and were then used for making electrical recordings.
Patch-clamp recordings of voltage-sensitive Na+ currents: Whole-cell voltage-clamp recordings were made using conventional patch-clamp technique (Hamill et al., Pfluegers Arch. 391:85-100 (1981)) with an Axopatch 200A amplifier (Axon Instruments, Foster City, Calif.). Recordings were made within 2-3 hours after neuron dissociation. The recording chamber was continuously superfused with Tyrode""s solution (156 mM NaCl, 3.5 mM KCl, 2 mM CaCl2, 5 mM NaHCO3, 10 mM HEPES, 10 mM glucose, pH 7.4) at a speed of about 1 ml/min. Thin-walled pipettes were pulled from 100-xcexcl Clay Adams Accu-Fill 90 Micropet disposable pipettes (Becton, Dickenson and Company, Parsipanny, N.J.), fire-polished and sylgarded (Dowxe2x80x94Coming, Midland, Mich.). The pipette resistances ranged from 1 to 3 Mxcexa9 when the pipettes were filled with internal solution containing (in mM): 130 CsF, 20 NaCl, 1 CaCl2, 2 MgCl2, 10 EGTA, 10 HEPES, pH adjusted to 7.4 with CsOH. Drugs and intervening wash-outs were applied through a linear array of flow pipes (Drummond Microcaps, 2-xcexcl, 64-mm length). Compounds are dissolved in dimethylsulfoxide (DMSO) to make a 10 mM stock solution, which was subsequently diluted into Tyrode""s solution to give final concentrations of 0.1-20 xcexcM. At the highest (1%) concentration. DMSO inhibited the size of Na+ current only slightly. Currents were recorded at room temperature (22-25xc2x0 C.), filtered at 5 kHz with 4-pole Bessel filter, digitized at 20-50-xcexcs intervals, and stored using Digidata 1200 analog/digital interface with Pclamp6/Clampex software (Axon Instruments). Residual series resistance ranged from 0.4 to 0.8 Mxcexa9 after partial compensation (typically xcx9c90%). The inhibitory potency of drugs was assessed by measuring reductions in the peak amplitude of Na30  currents induced by increasing concentrations of compounds tested. Na30  currents were elicited by stepping membrane voltage from holding potentials over the range xe2x88x92100 mV to xe2x88x9250 mV, to a pulse potential of xe2x88x9210 mV. The test pulse duration was 5-10 msec, repeated at a frequency xe2x89xa61 Hz. Concentration-inhibition curves were fitted with equation 1:
I/Icontrol=1/(1+([compound]/IC50))xe2x80x83xe2x80x83Eq. 1
where Icontrol is the maximal Na+ current in the absence of antagonist, [compound] is the drug concentration, and IC50 is the concentration of compound that produces half maximal inhibition.
Binding Assay
The ability of compounds of the present invention to modulate either site 1 or site 2 of the Na+ channel was determined following the procedures fully described in Yasushi, J. Biol. Chem. 261:6149-6152 (1986) and Creveling, Mol. Pharmacol. 23:350-358 (1983), respectively. Rat forebrain membranes were used as sources of Na+ channel proteins. The binding assays were conducted in 130 xcexcM choline chloride at 37xc2x0 C. for 60-minute incubation with [3H] saxitoxin and [3H] batrachotoxin as radioligands for site 1 and site 2, respectively.
The compounds of the present invention may be tested for in vivo anticonvulsant activity after iv or ip injection using a number of anticonvulsant tests in mice (audiogenic seizure model in DBA-2 mice, pentylenetetrazol-induced seizures in mice, maximum electroshock seizure test (MES)).
The compounds may be tested for their neuroprotective activity after focal and global ischemia produced in rats or gerbils according to the procedures described in Buchan et al. (Stroke, Suppl. 148-152 (1993)) and Sheardown et al. (Eur. J. Pharmacol. 236:347-353 (1993)) and Graham et al. (J. Pharmacol. Exp. Therap. 276:1-4 (1996)).
The compounds may be tested for their neuroprotective activity after traumatic spinal cord injury according to the procedures described in Wrathall et. al. (Exp. Neurology 137:119-126 (1996)) and Iwasaki et. al. (J. Neuro Sci. 134:21-25 (1995)).
Compositions within the scope of this invention include all compositions wherein the compounds of the present invention are contained in an amount which is effective to achieve its intended purpose. While individual needs vary, determination of optimal ranges of effective amounts of each component is within the skill of the art. Typically, the compounds may be administered to mammals, e.g. humans, orally at a dose of 0.0025 to 50 mg/kg, or an equivalent amount of the pharmaceutically acceptable salt thereof, per day of the body weight of the mammal being treated for epilepsy, neurodegenerative diseases, anesthesia, arrhythmia, manic depression, and pain. For intramuscular injection, the dose is generally about one-half of the oral dose.
In the method of treatment or prevention of neuronal loss in global and focal ischemia, brain and spinal cord trauma, hypoxia, hypoglycemia, status epilepsy and surgery, the compound can be administrated by intravenous injection at a dose of about 0.025 to about 10 mg/kg.
The unit oral dose may comprise from about 0.01 to about 50 mg, preferably about 0.1 to about 10 mg of the compound. The unit dose may be administered one or more times daily as one or more tablets each containing from about 0.1 to about 10, conveniently about 0.25 to 50 mg of the compound or its solvates.
In addition to administering the compound as a raw chemical, the compounds of the invention may be administered as part of a pharmaceutical preparation containing suitable pharmaceutically acceptable carriers comprising excipients and auxiliaries which facilitate processing of the compounds into preparations which can be used pharmaceutically. Preferably, the preparations, particularly those preparations which can be administered orally and which can be used for the preferred type of administration, such as tablets, dragees, and capsules, and also preparations which can be administered rectally, such as suppositories, as well as suitable solutions for administration by injection or orally, contain from about 0.01 to 99 percent, preferably from about 0.25 to 75 percent of active compound(s), together with the excipient.
Also included within the scope of the present invention are the non-toxic pharmaceutically acceptable salts of the compounds of the present invention. Acid addition salts are formed by mixing a solution of the particular 2-aminoacetamide of the present invention with a solution of a pharmaceutically acceptable non-toxic acid such as hydrochloric acid, flumaric acid, maleic acid, succinic acid, acetic acid, citric acid, tartaric acid, carbonic acid, phosphoric acid, oxalic acid, dichloroacetic acid, and the like. Basic salts are formed by mixing a solution of the particular 2-aminoacetamide of the present invention with a solution of a pharmaceutically acceptable non-toxic base such as sodium hydroxide, potassium hydroxide,. choline hydroxide, sodium carbonate and the like.
The pharmaceutical compositions of the invention may be administered to any animal which may experience the beneficial effects of the compounds of the invention. Foremost among such animals are mammals, e.g., humans, although the invention is not intended to be so limited.
The pharmaceutical compositions of the present invention may be administered by any means that achieve their intended purpose. For example, administration may be by parenteral, subcutaneous, intravenous, intramuscular, intraperitoneal, transdermal, or buccal routes. Alternatively, or concurrently, administration may be by the oral route. The dosage administered will be dependent upon the age, health, and weight of the recipient, kind of concurrent treatment, if any, frequency of treatment, and the nature of the effect desired.
The pharmaceutical preparations of the present invention are manufactured in a manner which is itself known, for example, by means of conventional mixing, granulating, dragee-making, dissolving, or lyophilizing processes. Thus, pharmaceutical preparations for oral use can be obtained by combining the active compounds with solid excipients, optionally grinding the resulting mixture and processing the mixture of granules, after adding suitable auxiliaries, if desired or necessary, to obtain tablets or dragee cores.
Suitable excipients are, in particular, fillers such as saccharides, for example lactose or sucrose, mannitol or sorbitol, cellulose preparations and/or calcium phosphates, for example tricalcium phosphate or calcium hydrogen phosphate, as well as binders such as starch paste, using, for example, maize starch, wheat starch, rice starch, potato starch, gelatin, tragacanth, methyl cellulose, hydroxypropylmethylcellulose, sodium carboxymethylcellulose, and/or polyvinyl pyrrolidone. If desired, disintegrating agents may be added such as the above-mentioned starches and also carboxymethyl-starch, cross-linked polyvinyl pyrrolidone, agar, or alginic acid or a salt thereof, such as sodium alginate. Auxiliaries are, above all, flow-regulating agents and lubricants, for example, silica, talc, stearic acid or salts thereof, such as magnesium stearate or calcium stearate, and/or polyethylene glycol. Dragee cores are provided with suitable coatings which, if desired, are resistant to gastric juices. For this purpose, concentrated saccharide solutions may be used, which may optionally contain gum arabic. talc, polyvinyl pyrrolidone, polyethylene glycol and/or titanium dioxide, lacquer solutions and suitable organic solvents or solvent mixtures. In order to produce coatings resistant to gastric juices, solutions of suitable cellulose preparations such as acetyl-cellulose phthalate or hydroxypropylmethyl-cellulose phthalate, are used. Dye stuffs or pigments may be added to the tablets or dragee coatings, for example, for identification or in order to characterize combinations of active compound doses.
Other pharmaceutical preparations which can be used orally include push-fit capsules made of gelatin, as well as soft, sealed capsules made of gelatin and a plasticizer such as glycerol or sorbitol. The push-fit capsules can contain the active compounds in the form of granules which may be mixed with fillers such as lactose, binders such as starches, and/or lubricants such as talc or magnesium stearate and, optionally, stabilizers. In soft capsules, the active compounds are preferably dissolved or suspended in suitable liquids, such as fatty oils, or liquid paraffin. In addition, stabilizers may be added.
Possible pharmaceutical preparations which can be used rectally include, for example, suppositories, which consist of a combination of one or more of the active compounds with a suppository base. Suitable suppository bases are, for example, natural or synthetic triglycerides, or paraffin hydrocarbons. In addition, it is also possible to use gelatin rectal capsules which consist of a combination of the active compounds with a base. Possible base materials include, for example, liquid triglycerides, polyethylene glycols, or paraffin hydrocarbons.
Suitable formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form, for example, water-soluble salts and alkaline solutions. In addition, suspensions of the active compounds as appropriate oily injection suspensions may be administered. Suitable lipophilic solvents or vehicles include fatty oils, for example, sesame oil, or synthetic fatty acid esters, for example, ethyl oleate or triglycerides or polyethylene glycol-400 (the compounds are soluble in PEG400). Aqueous injection suspensions may contain substances which increase the viscosity of the suspension include, for example, sodium carboxymethyl cellulose, sorbitol, and/or dextran. Optionally, the suspension may also contain stabilizers.
The following examples are illustrative, but not limiting, of the method and compositions of the present invention. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in clinical therapy and which are obvious to those skilled in the art are within the spirit and scope of the invention.